Vacuum tube



Aug. 21, 1928.

C. E. FITCH "VACUUM TUBE Filed 001;. 30, 1925 Patented Aug. 21, 1928.

UNITED STATES CLAUDE E. FITCH, F WILMETTE, ILLINOIS.

vacuum TUBE.

Application filed October 30, 1925. Serial No. 65,774.

My invention relates to vacuum tubes and methodof making the same and to a machine for making certain portions of such vacuum tubes.

o It is a purpose of m invention to provide a vacuum tube, or ot er glass vessel from which the air has been exhausted, that is not provided with an exposure tip where the exhausting operation was carried out and which was afterwards sealed oif. In order to provide for the exhausting of the air from such a device through the base portion thereof, an exhaust tube is provided that extends into the interior of said vessel or vacuum tube from the base or stem end thereof which has a free and unrestricted passage from end to end thereof, and which is sealed ofl after the air is exhausted from the vacuum tube, or other vessel from which the air has been exhausted, where the same projects through the stem end of said vessel.

It is another purpose of the invention to provide a new and improved vacuum-tube having a plurality of elements provided with supporting wires that are mounted in a stem portion having an annular pro'ection in which said wires are mounted. aid wires are. preferably mounted in a circular series and may be mounted in unequally spaced relation. This unequal spacing is ver important in constructingtubes of high efficiency for low wave lengths as by the unequal spacing, the capacity due to the proximity of the supportin members particularly those actin as conductors, is decreased by spacing those aving a capacity relation to each other at a greater distance from each other than those having a conductive relation to each other. Thus, the filament support wires may be closely spaced, while the grid and plate support wires and the conductors should be spaced at a greater distance.

It is another important purpose of the invention to provide a mountin for the elements in a vacuum tube where y any warping or distortion of the same out of normal position is avoided by placing the supportingmembers so that they do notall'lie 1n the same plane. In this way, the supportlng members can be made to brace each other, this being .particularly important in connection with the plate element, the supporting wires for the plate element beingtprefera 1y arranged on a triangle so that the three supporting wires do not lie in the same plane,

thus making a very rigid supporting structure for the plate element.

Other objects and advantages of the invention will appear as the description of the accompanying drawings proceeds. However, I desire to have it distinctly understood that I do not intend to limit myself to the exact details shown or described, but that I intend to include as part of my invention all such obvious changes and modifications of parts as would occur to a personskilled in this art and as would fall within the scope of the claims.

In the drawings:

Fig. 1 is a diagrammatic view partly in section showing the stem forming tube, the exhaust tube and the wires in their relative positions before the compressing opera-tion takes place;

Fig. 2 is a similar view showing the parts after the same have been united with the core and jaws shown diagrammatically;

Fig. 3 is a fragmentary sectional view showing the stem portion sealed in the end of the vacuum tube and exhaust tube sealed off; a

Fig. 4 is an end view of the parts shown in Fig. 1 as the same would appear when viewed from the bottom of Fig. 1; I

Fig. 5 is a. similar view of the parts as shown in Fig. 2;

Fig. 6 is a. perspective view of a vacuum tube embodying my invention showing a dif-j ferent arrangement of the supporting wires from that shown in Figs. 4 and 5.; and

Fig. 7 is an end view of the tube shown 1n Fig. 6 with the base thereof omitted.

Referring now to Fig. 1, my improved method of making a stem for a vacuum tube, or other glass vessel from which the air s exhausted, provided with an exhaust tube is practiced by mounting the parts substantially as shown in Fig. 1. Any suitable means may be provided for supporting the same. The

wires 46 are mounted with the ends thereof to which the wires 88 are secured extending a short distance between the tubes 73 and 64 and preferably in engagement with the widened portion 65 of the tube 64. The parts are then heated uniformly at the lower end of the member 73 and the widened portion 65 of the member 64, the zone in which the'parts are heated embracing substantially the entire widened portion 65 of the member 64 and the portion of the. member 73 opposite thereto. This heating is continued until the glass tubes in the heated zone thereof reach substantially diameter due to the fact that the weight of the glass tends to draw the same downward. The mandrel or core 48 is made slightly larger than the internal diameter of the member 65 and the member 65 will" practically always be of smaller diameter than the core 48 after the same has been heated due to such reduction of the diameter of the same because of being heated. The core 48 is, however, provided with a tapered nose to spread theportion 65 outwardly and increase the diameter thereof as the core 48 is projected into the same.

After the members 73 and 65 have been heated to the'proper extent, the mandrel or core 48 is inserted and jaws or dies are applied to the exterior thereof to thus compress the members 65 and 73 between the core 48 and the jaws with the wires 46 therebetween. The portions of the members 7 3 and 65 engaged by the jaws 33 and by the core 48 being in a plastic state, the same will be united into an annular joint indicated by the numeral 89 which acts as an anchoring means for the wires 46, the berated co per clad wires 88 being fused in and seale in the joint 89 so that the entire joint with the wires therein is air tight, the joint being of smaller external diameter than the original external diameter of the tube 7 3 due to the compressing action of the jaws and being of larger internal di-- ameter' than the tubular portion 65 of the member 64 due to the expanding-action of the core 48. Due to the shape of the jaws, an.

annular shoulder 90 is formed between the portion 89 and the tubular portion 73. The wires are arranged in an annular series, as will be evident from Fig. 4, before the compressin operation takes place and will be sealed in the annular portion 89 in such a series as shown in Fig. 5.

In Fig. 3 the stem member, after the same has been made into a unit as shown in Fig. 2, is assembled with the tubular body portion 91 01? the vacuum tube, or other glass vessel belng joined in a plastic state with a reduced end 92 of said tubular member 91 at the flared portion 74 thereof in a well known manner. It will be noted that a free and unrestricted passage extends through the tube 64, the same elng'indicated by the numeral 93 in Fig. 2 after the joint between the members 64 and 73 15 completed and that due tothe provision of the annular joint 89, the wires 88 are sealed and the wires 46 are firmly embedded in the 'oint' 89 without in any way restricting or interfering with the passage 93, the same being, in fact, enlarged as indicated at 94 at said annular joint 89. The air is then exhausted from the chamber 95 within the tube 91 in'the usual well known manner by attaching a suitable flexible tube to the tubular member 64 outside the member 91 and after the air has been exhausted from the chamber 95, the tube 64 is sealed off at 96, this sealed ofi portion 96 being within the base of the finished tube and being thus hidden.

A completed tube is shown in Figs. 6 and 7 and is indicated by the numeral 91, being in all respects like the'tube 90 except that the wires are mounted in unequally spaced relation in the annular joint 89 instead of in the evenly spaced manner shown in Fig. 5. The tube 91 is shown as having a plate element 96, a grid element 97 and a filament 98 therein. The filament 98 is supported from a glass head 99 provided on the transverse member 100 on the supporting frame 101 for the grid. The ends of the filament 98 are secured in conducting relation with the. supporting and conducting wires 102 mounted in the annu ar anchoring portion 89 of the stem. The plate 96 is provided with the supportin wires or members 103 and the supporting and conducting member 104. The id support 101 terminates in a pair of mem ers 105 and 106, the member being a conducting and supporting member and the member 106 being merely a supporting member.

It will be seen from Figs. 6 and 7 that the members 102 are relatively close together, while the members 104 and 105 are spaced a relatively greater distance from each other and from the members 102 and furthermore, that the members 103 and 106 which are merely supporting members, are also spaced at a greater distance from each other and from the members 104, 105 and 102 than the members 102 are from each other. As the members 102 are in conductive relation to each other, it is immaterial how close the same are to each other as lon as they do not touch, as the arrangement 0 the wires in a circular series and the unequal spacing thereof are both used to reduce the internal capacity between the leads and the sup orts immediately adjacent each other. e other members all have a capacitative relation to each other and to the members 102, accordingly, the widest possible spacing for the same is desirable. By the arrangement of the wires 46 or the wires 102, 103, 104 and 105 in a circular series, a much wider spacing is obtained than if the same were all in a row as has been a common arrangement prior to my invention. Furthermore, by the arrangement of the wires in a circular series, the mem- Ill .aaeneae on the vertices of a triangle which gives the maximum supporting strength for the plate element 96 and prevents the some from twisting or Warping out of proper upright posi tion and maintains the spacing between the parts substantially uniform .LhiS is a. great advantage over having all the supporting members lie in the same plane as there is little strength to the supporting means in a direc tion transverse to this plane.

Having'thus described my invention What i desire to claim and secure by United States Letters Patent is:

1. In a sealed glass vessel of the character described, a bulb portion, a stem portion ex tending inwardly from one end thereof, an exhaust tube joined integrally to said stem portion at the inner end thereof and open at its inner end to form an annular Wire are shoring portion and an annular series of Wires sealeol in said. annular Wire anchoring portion.

52. in a sealleol glass vessel of the character describedl, a buih portion, a stem portion extending inwardiy from one end thereof, an exhaust tube joined integrally to said stern portion at the inner end thereof and open at its inner end to form an annular Wire anohoring portion and a circular series of unequally spaced Wires 'sealeii in said annular wire anchoring portion.

In Witness whereof, I hereunto subscribe my name this 10th day of @ctober A. 10., 1925.

station n. rrron.

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